Lens barrel, imaging device body, and imaging device

ABSTRACT

There are provided a lens barrel, an imaging device body, and an imaging device that can reduce a deviation in a blurred image of oblique luminous flux caused by an APD filter. 
     A lens barrel includes a first lens optical system and a second lens optical system serving as lens optical systems including focus lenses, a diaphragm that changes the amount of an incident ray and emits the incident ray, a first APD filter that is disposed on a light-incident side of the diaphragm, and a second APD filter that is disposed on a light-emitting side of the diaphragm. Since the amount of a reduced upper ray L 1  of oblique luminous flux and the amount of a reduced lower ray L 2  thereof are made to be substantially equal to each other by the first APD filter and the second APD filter, a deviation of a blurred image is reduced.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 15/452,735, filed on 8 Mar. 2017, now pending, which claimspriority from PCT International Application PCT/JP2015/074047 filed on26 Aug. 2015, which claims priority under 35 USC 119(a) from JapanesePatent Application No. 2014-184852 filed on 11 Sep. 2014. The aboveapplications are hereby expressly incorporated by reference, in itsentirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a lens barrel, an imaging device body,and an imaging device that include an apodization filter.

2. Description of the Related Art

There is known an imaging device that includes an apodization filter(hereinafter, referred to as an APD filter) having opticalcharacteristics in which light transmittance is reduced as a distancefrom an optical axis is increased (see JP1997-236740A (JP-H09-236740A)and JP2012-128151A). The APD filter reduces the amount of a ray aroundonly a blurred image (spotlight blurring or the like), which is out offocus, without reducing the amount of a ray around an image plane.Accordingly, the APD filter realizes a beautiful blur by applyinggradation to the profile of the blurred image.

In the imaging device including the APD filter, the APD filter isdisposed near a diaphragm (see JP-H09-236740A) and JP2012-128151A). InJP1997-236740A (JP-H09-236740A), the APD filter is disposed near thediaphragm on the light-incident side or the light-emitting side of thediaphragm in order to reduce the vignetting of a ray deviating from theoptical axis. In JP2012-128151A, the APD filter is disposed near thediaphragm on the light-emitting side of the diaphragm in order to reducethe dependency of an angle with respect to the optical axis of luminousflux of incident rays on the effect of the APD filter.

Since the APD filter cannot be disposed at the same position as thediaphragm in principle even though the APD filter is disposed near thediaphragm as disclosed in JP1997-236740A (JP-H09-236740A) andJP2012-128151A, the APD filter is disposed at a position that is shiftedfrom the diaphragm in the direction of the optical axis. In a case inwhich incident luminous flux is parallel to the optical axis, an upperray and a lower ray of the luminous flux (parallel luminous flux) areincident on positions of the APD filter that have the same lighttransmittance. Accordingly, the APD filter uniformly applies gradationto the profile of a blurred image. In contrast, in a case in whichincident luminous flux is not parallel to the optical axis, an upper rayand a lower ray of the luminous flux (oblique luminous flux) areincident on positions of the APD filter that have different lighttransmittances. Accordingly, the APD filter non-uniformly appliesgradation to the profile of a blurred image. As a result, a deviation isgenerated in the blurred image.

The generation of a deviation in a blurred image in the case of obliqueluminous flux will be described with reference to FIG. 11. In FIG. 11,an APD filter 118 is disposed on the light-emitting side of a diaphragm116 and oblique luminous flux, which is obliquely incident on thediaphragm 116 from the upper side of an optical axis, is shown.

In this case, an upper ray L102, which passes through an upper end ofthe aperture portion of the diaphragm 116, passes through a positionthat is closer to the center of the APD filter 118 than the positionthrough which an upper ray of parallel luminous flux passes. On theother hand, a lower ray L103, which passes through a lower end of theaperture portion of the diaphragm 116, passes through a position that ismore distant from the center of the APD filter 118 than the positionthrough which a lower ray of parallel luminous flux passes. The centerof the APD filter 118 corresponds to the optical axis and the lighttransmittance of the APD filter 118 is reduced as a distance from thecenter of the APD filter 118 is increased. Accordingly, the amount ofthe upper ray L102 reduced by the APD filter 118 is smaller than theamount of the lower ray L103 reduced by the APD filter 118. Accordingly,a deviation is generated in a blurred image of the oblique luminous fluxin a vertical direction.

SUMMARY OF THE INVENTION

An object of the invention is to provide a lens barrel, an imagingdevice body, and an imaging device that can reduce a deviation of ablurred image of oblique luminous flux caused by an APD filter.

A lens barrel of the invention comprises a lens optical system, adiaphragm, a first APD filter, and a second APD filter. The lens opticalsystem includes a focus lens forming an image with an incident ray. Thediaphragm changes the amount of the incident ray and emits the incidentray. The first APD filter is disposed on a light-incident side of thediaphragm. The second APD filter is disposed on a light-emitting side ofthe diaphragm.

It is preferable that the first and second APD filters have opticalcharacteristics in which light transmittance is reduced toward an outerperipheral portion from an optical axis and the optical characteristicsof the first APD filter are the same as the optical characteristics ofthe second APD filter. It is preferable that a first optical distancebetween the diaphragm and the first APD filter is equal to a secondoptical distance between the diaphragm and the second APD filter.

Not only a case in which a component of the lens optical system ispresent between the first and second APD filters but also a case inwhich a component of the lens optical system is not present between thefirst and second APD filters is preferable.

Further, it is preferable that two sets of the first and second APDfilters are provided, a component of the lens optical system is notpresent between one set of the first and second APD filters, and acomponent of the lens optical system is present between the other set ofthe first and second APD filters.

It is preferable that the lens barrel further comprises a filterinsertion/retreat unit in a case in which the lens barrel comprises twosets of the first and second APD filters. The filter insertion/retreatunit inserts and retreats each of one set of the first and second APDfilters and the other set of the first and second APD filters.Alternatively, it is preferable that each of one set of the first andsecond APD filters and the other set of the first and second APD filtersis an APD filter of which optical characteristics are changed by achange in shape, and the lens barrel further comprises a shape changingunit provided for each APD filter and changing the shape of each APDfilter.

The lens barrel is detachably mounted on an imaging device body of theinvention, and the imaging device body comprises an imaging element thatgenerates an imaging signal by photoelectrically converting a ray havingpassed through the first and second APD filters.

An imaging device of the invention comprises the lens barrel and theimaging device body.

Further, an imaging device of the invention comprises a lens opticalsystem, a diaphragm, a first APD filter, a second APD filter, and animaging element. The lens optical system includes a focus lens formingan image with an incident ray. The diaphragm changes the amount of theincident ray and emits the incident ray. The first APD filter isdisposed on a light-incident side of the diaphragm. The second APDfilter is disposed on a light-emitting side of the diaphragm. Theimaging element generates an imaging signal by photoelectricallyconverting a ray having passed through the first and second APD filters.

According to the invention, since an upper ray and a lower ray can bereduced without a deviation by a first APD filter disposed on thelight-incident side of a diaphragm and a second APD filter disposed onthe light-emitting side of the diaphragm, a deviation in blurring causedby the APD filters can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the configuration of an imaging device.

FIG. 2 is a graph showing the optical characteristics of an APD filter.

FIG. 3 is a view showing the light path of parallel luminous flux andthe light path of oblique luminous flux.

FIG. 4 is a view showing the amount of a ray of oblique luminous fluxthat is reduced by first and second APD filters.

FIG. 5 is a view showing the light path of parallel luminous flux andthe light path of oblique luminous flux that are regulated by first andsecond lens optical systems.

FIG. 6 is a diagram showing the configuration of a lens barrel of asecond embodiment.

FIG. 7 is a view showing the optical characteristics of an APD filter ofthe second embodiment.

FIG. 8 is a view showing the amount of a ray of oblique luminous fluxthat is reduced by first and second APD filters of the secondembodiment.

FIG. 9 is a view showing the configuration of an imaging device of athird embodiment.

FIG. 10 is a view showing the configuration of an imaging device of afourth embodiment.

FIG. 11 is a view showing the amount of a ray of oblique luminous fluxthat is reduced by an APD filter in the related art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

In FIG. 1, a lens barrel 10 of a first embodiment of the invention isdetachably mounted on an imaging device body 20, and the lens barrel 10and the imaging device body 20 are used as an imaging device 30. In theevent that a base end portion 10A of the lens barrel 10 is mounted on alens barrel mounting portion 20A of the imaging device body 20, the lensbarrel 10 and the imaging device body 20 are connected to each other.The base end portion 10A and the lens barrel mounting portion 20A areprovided with electrical contacts 10B and 20B, respectively. The lensbarrel 10 and the imaging device body 20 are electrically connected toeach other through the electrical contacts 10B and 20B.

The lens barrel 10 includes a first lens optical system 12, a secondlens optical system 13, a diaphragm 16, a first apodization filter (APDfilter) 17, and a second APD filter 18. All of the first lens opticalsystem 12, the second lens optical system 13, the diaphragm 16, thefirst APD filter 17, and the second APD filter 18 are disposed on anoptical axis LA of the lens barrel 10.

Each of the first and second lens optical systems 12 and 13 includes afocus lens that forms an image with an incident ray. The first lensoptical system 12 is disposed closer to the light-incident side than thesecond lens optical system 13. The diaphragm 16 is disposed between thefirst and second lens optical systems 12 and 13. The diaphragm 16changes the amount of an incident ray, and emits the ray.

The first APD filter 17 is disposed between the first lens opticalsystem 12 and the diaphragm 16. The second APD filter 18 is disposedbetween the diaphragm 16 and the second lens optical system 13. Only thediaphragm 16 is present between the first and second APD filters 17 and18, and other components are not present between the first and secondAPD filters 17 and 18.

The imaging device body 20 includes an imaging element 21, an imageprocessing unit 23, a control section 24, a display unit 25, and amemory 26. The imaging element 21 generates imaging signals byphotoelectrically converting an incident ray entering from the lensbarrel 10. The imaging signals are output to the image processing unit23. The imaging element 21 is, for example, a CMOS (Complementary MetalOxide Semiconductor) image sensor or a CCD (Charge Coupled Device) imagesensor, and can control an electronic shutter speed.

The image processing unit 23 generates a photographed image from theimaging signals, and outputs the photographed image to the display unit25 and the memory 26. The display unit 25 displays the photographedimage that is input from the image processing unit 23. The memory 26stores the photographed image that is input from the image processingunit 23. Further, the image processing unit 23 supplies a brightnesssignal, which is obtained from the imaging signal by the Y/C conversionor the like, to the control section 24.

The control section 24 includes an exposure control unit 28 and afocusing control unit 29. The exposure control unit 28 calculates aphotometric value (performs photometry) on the basis of the brightnesssignal that is supplied from the image processing unit 23. The exposurecontrol unit 28 obtains an appropriate exposure value by performingpredetermined calculation on the basis of the calculated photometricvalue. The exposure control unit 28 determines a set of an imagingdiaphragm value and an imaging shutter speed on the basis of thisappropriate exposure value. The exposure control unit 28 sets an imagingexposure by setting the imaging diaphragm value and the imaging shutterspeed on the diaphragm 16 and the imaging element 21, respectively.

A substantial diaphragm value, which is corrected in consideration ofnot a diaphragm value determined depending on the effective aperturediameter of the diaphragm 16 but the light transmittance of the firstand second APD filters 17 and 18 in an effective aperture region, isused for the determination of an imaging exposure that is performed bythe exposure control unit 28. The light transmittance in the effectiveaperture region is calculated by the product of the light transmittanceT₁ of the first APD filter 17 and the light transmittance T₂ of thesecond APD filter 18 in the effective aperture region.

The focusing control unit 29 performs auto-focusing control. Thefocusing control unit 29 determines a focus search range that is a rangein which a focus position is searched and a search interval that is aninterval at which a focus position is searched. The focusing controlunit 29 determines focusing evaluation positions on the basis of thefocus search range and the search interval.

The focusing control unit 29 moves all or a part of the first and secondlens optical systems 12 and 13 to the respective focusing evaluationpositions and acquires focusing evaluation values from the imageprocessing unit 23 at the respective focusing evaluation positions.High-frequency components are extracted from the imaging signals and areintegrated, so that the focusing evaluation values are obtained. Thefocusing control unit 29 detects a focus position where the focusingevaluation value is largest from the focusing evaluation values, whichare obtained at the respective focusing evaluation positions, and setsthe positions of the first and second lens optical systems 12 and 13 tothe detected focus position.

The focusing control unit 29 can focus on a near subject from a subject,which is positioned at infinity, by feeding the first and second lensoptical systems 12 and 13 and moving the second lens optical system 13.

Since the diaphragm 16, which is provided in the lens barrel 10, isdisposed substantially in the middle of a gap between the first andsecond APD filters 17 and 18, a distance (a first distance) between thefirst APD filter 17 and the diaphragm 16 is equal to a distance (asecond distance) between the diaphragm 16 and the second APD filter 18.Here, the fact that the first and second distances are equal to eachother means that a difference between the first and second distances is10% or less of the first or second distance, preferably means that thedifference therebetween is 5% or less of the first or second distance,and more preferably means that the difference therebetween is 3% or lessof the first or second distance.

Further, since the components of the lens optical systems are notpresent between the first and second APD filters 17 and 18, an opticaldistance (a first optical distance) D1 between the first APD filter 17and the diaphragm 16 is equal to the first distance and an opticaldistance (a second optical distance) D2 between the diaphragm 16 and thesecond APD filter 18 is equal to the second distance as shown in FIG. 4.

The optical characteristics of the first APD filter 17 are the same asthe optical characteristics of the second APD filter 18. As shown inFIG. 2, the first and second APD filters 17 and 18 have opticalcharacteristics in which light transmittance T is reduced as a distancefrom the optical axis LA is increased toward the outer peripheralportion of each APD filter (as an image height H is increased). That is,the amount of a reduced light, which is incident on the first and secondAPD filters 17 and 18, is increased as the image height H is increased.

Here, the fact that the optical characteristics of the first APD filter17 are the same as the optical characteristics of the second APD filter18 means that a difference between the light transmittance of the firstAPD filter 17 and the light transmittance of the second APD filter 18 is10% or less of the light transmittance of the first or second APD filter17 or 18, preferably means that the difference therebetween is 5% orless of the light transmittance of the first or second APD filter 17 or18, and more preferably means that the difference therebetween is 3% orless of the light transmittance of the first or second APD filter 17 or18, at an arbitrary image height.

The total light transmittance of the first and second APD filters 17 and18 is calculated by the product of the light transmittance T₁ of thefirst APD filter 17 and the light transmittance T₂ of the second APDfilter 18 on the light path of an incident ray. Here, the lighttransmittance T₁ and the light transmittance T₂ on the light path havedifferent values in regard to an incident ray (oblique luminous flux)passing through the lens barrel 10 so as to be oblique to the opticalaxis LA.

Next, since the first and second lens optical systems 12 and 13 deviatefrom the focus position, the light-reducing effects of the first andsecond APD filters 17 and 18, which are obtained in a case in which ablurred image is generated, will be described with reference to FIGS. 3and 4.

In FIG. 3, the luminous flux (parallel luminous flux) of incident raysparallel to the optical axis LA forms an image at a point F1 on theoptical axis LA. Since an upper ray of the parallel luminous flux isincident on a position where light transmittance is equal to the lighttransmittance T of the first APD filter 17 and a lower ray of theparallel luminous flux is incident on a position where lighttransmittance is equal to the light transmittance of the second APDfilter 18, the amount of a ray reduced by the first APD filter 17 andthe amount of a ray reduced by the second APD filter 18 are equal toeach other. Accordingly, a deviation is not generated in a blurred imagethat is generated by the parallel luminous flux.

The luminous flux (oblique luminous flux) of incident rays, which areincident so as to be oblique to the optical axis LA from the top, formsan image at a point F2 that deviates from the optical axis LA.Specifically, as shown in FIG. 4, a main ray L1 of the oblique luminousflux passes through a portion of the first APD filter 17 that is distantfrom the optical axis LA by a distance H11 and a portion of the secondAPD filter 18 that is distant from the optical axis LA by a distanceH21. An upper ray L2 passes through a portion of the first APD filter 17that is distant from the optical axis LA by a distance H12 and a portionof the second APD filter 18 that is distant from the optical axis LA bya distance H22. A lower ray L3 passes through a portion of the first APDfilter 17 that is distant from the optical axis LA by a distance H13 anda portion of the second APD filter 18 that is distant from the opticalaxis LA by a distance H23.

The distance H12 and the distance H23 are equal to each other, and thedistance 1113 and the distance 1122 are equal to each other. Since theoptical characteristics of the first APD filter 17 are the same as theoptical characteristics of the second APD filter 18 and the firstoptical distance D1 and the second optical distance D2 are equal to eachother, the transmittances of the APD filters satisfy relationalequations expressed by Equation (1) and Equation (2).

T ₂(H12)=T ₂(H23)  Equation (1)

T ₂(H22)=T ₁(H13)  Equation (2)

Here, T₁(H) denotes the light transmittance of the first APD filter 17at the image height H. T₂(H) denotes the light transmittance of thesecond APD filter 18 at the image height H.

Equation (3) is derived from Equation (1) and Equation (2). The leftside of Equation (3) represents the transmittance of the first andsecond APD filters 17 and 18 on the light path of the upper ray L2, andthe right side thereof represents the transmittance of the first andsecond APD filters 17 and 18 on the light path of the lower ray L3.

T ₁(H12)×T ₂(H22)=T ₁(H13)×T ₂(H23)  Equation (3)

That is, since the amount of the reduced upper ray L2 and the amount ofthe reduced lower ray L3 are equal to each other, a deviation is notgenerated in a blurred image that is generated by the oblique luminousflux.

Since the diaphragm 16 is disposed between the first and second APDfilters 17 and 18 as described above, the amount of an upper ray reducedby the first APD filter 17 is equal to the amount of a lower ray reducedby the second APD filter 18 regardless of an angle between incidentluminous flux and the optical axis LA. For this reason, a beautifulblurred image is obtained in the imaging device 30 regardless of anangle between incident luminous flux and the optical axis LA.

The first distance and the second distance have been equal to eachother, the first optical distance D1 and the second optical distance D2have been equal to each other, and the optical characteristics of thefirst APD filter 17 have been the same as the optical characteristics ofthe second API) filter 18 in the first embodiment; but the invention isnot limited to this aspect. The first and second distances, the firstand second optical distances D1 and D2, and the optical characteristicsof the first and second APD filters 17 and 18 may be appropriatelydesigned so that the amount of the reduced upper ray of the obliqueluminous flux is equal to the amount of the reduced lower ray thereof.

For example, the various distances and the optical characteristics,which have been described above, may be appropriately designed so thatan upper ray and a lower ray are optically symmetrical to each otherwith respect to a point positioned on the diaphragm 16 and the opticalaxis LA in a region between the first and second APD filters 17 and 18.Here, the fact that the amount of the reduced upper ray and the amountof the reduced lower ray are substantially equal to each other meansthat a difference between the amount of the reduced upper ray and theamount of the reduced lower ray is 10% or less of the amount of thereduced upper ray or the reduced lower ray, preferably means that thedifference therebetween is 5% or less of the amount of the reduced upperray or the reduced lower ray, and more preferably means that thedifference therebetween is 3% or less of the amount of the reduced upperray or the reduced lower ray.

Further, it has been possible to focus on a near subject from a subject,which is positioned at infinity, by feeding the first and second lensoptical systems 12 and 13 and moving the second lens optical system 13in the first embodiment, but the invention is not limited to this aspectand can also use any focusing method. For example, a method of detectinga phase difference using phase-difference pixels can be used.

Furthermore, the upper ray and the lower ray of the first embodiment arerays that are positioned at end portions of the luminous flux regulatedby the diaphragm 16, but the upper ray and the lower ray are the sameeven in a case in which the luminous flux is regulated by the first andsecond lens optical systems 12 and 13.

In a case in which the diaphragm is close to the open state, the lightpath of an incident ray is regulated by not the diaphragm 16 but thefirst and second lens optical systems 12 and 13 as shown in FIG. 5.Parallel luminous flux forms an image at a point F3 on the optical axisLA. Since the amount of the reduced upper ray of the parallel luminousflux and the amount of the reduced lower ray thereof are equal to eachother as in the first embodiment, a deviation is not generated in ablurred image that is generated by the parallel luminous flux.

Oblique luminous flux forms an image at a point F4 that deviates fromthe optical axis LA. An upper ray of the oblique luminous flux isregulated by the first lens optical system 12, and a lower ray thereofis regulated by the second lens optical system 13. Since the amount ofthe reduced upper ray and the amount of the reduced lower ray are equalto each other as in the first embodiment in a case in which a main raypasses through a portion of the diaphragm near the optical axis LA, adeviation is not generated in a blurred image. It is preferable that thefirst and second lens optical systems 12 and 13 are designed so that themain ray of the oblique luminous flux passes through a portion of thediaphragm near the optical axis LA.

Second Embodiment

Components of the lens optical systems are not interposed between thediaphragm 16 and the first APD filter 17 and between the diaphragm 16and the second APD filter 18 in the first embodiment, but components ofthe lens optical system may be interposed at least one of between thediaphragm 16 and the first APD filter 17 and between the diaphragm 16and the second APD filter 18.

In FIG. 6, a lens barrel 35 of a second embodiment includes a first APDfilter 37 and a second APD filter 38. The first APD filter 37 isdisposed on the light-incident side of a first lens optical system 12.The second APD filter 38 is disposed on the light-emitting side of asecond lens optical system 13. That is, the first lens optical system 12is interposed between a diaphragm 16 and the first APD filter 37, andthe second lens optical system 13 is interposed between the diaphragm 16and the second APD filter 38. In the second embodiment, a first distancethat is an actual distance between the diaphragm 16 and the first APDfilter 37 is different from a first optical distance D1. Likewise, asecond distance that is an actual distance between the diaphragm 16 andthe second APD filter 38 is different from a second optical distance D2.

The first APD filter 37 is larger than the second APD filter 38. Thesize of the first APD filter 37 is determined according to the size ofthe incident surface of the lens barrel 35 or the size of the first lensoptical system 12. A ratio of the size (diameter) of the first APDfilter 37 to the size of the second APD filter 38 is substantially equalto a ratio of the first optical distance D1 to the second opticaldistance D2.

The optical characteristics of the first APD filter 37 and the opticalcharacteristics of the second APD filter 38 are similar to each other,and the first APD filter 37 and the second APD filter 38 have opticalcharacteristics shown in FIG. 7. Here, the fact that the opticalcharacteristics of the APD filters are similar to each other means thatthe first APD filter 37 and the second APD filter 38 correspond to eachother in terms of the distribution of light transmittance T obtained inthe event that a radius where the light transmittance of the APD filteris “0” is standardized as an image height “1”.

The rate of change of light transmittance T between a region(high-transmittance region), which has high light transmittance T and ispositioned near an optical axis, and a region (low-transmittanceregion), which has low light transmittance T and is positioned at anouter peripheral portion distant from the optical axis, of each of thefirst and second APD filters 37 and 38 of the second embodiment ishigher than that of each of the first and second APD filters 17 and 18of the first embodiment. That is, each of the first and second APDfilters 37 and 38 of the second embodiment is formed of an APD filter(hereinafter, referred to as a dichotomized filter) that issubstantially divided into the high-transmittance region and thelow-transmittance region. Since other structures of the secondembodiment are the same as those of the first embodiment, the detaileddescription thereof will be omitted.

Oblique luminous flux, which is regulated by the first and second lensoptical systems 12 and 13 and is inclined with respect to an opticalaxis LA from above at an inclination angle, will be described withreference to FIG. 8. An upper ray L6 of the oblique luminous flux isregulated by the first lens optical system 12 and a lower ray L7 thereofis regulated by the second lens optical system 13. The oblique luminousflux passes through a substantially upper region of the first APD filter37; passes through the first lens optical system 12, the diaphragm 16,and the second lens optical system 13 in this order; and passes througha substantially lower region of the second APD filter 38.

A main ray L5 of the oblique luminous flux passes through a portion(high-transmittance region) of the first APD filter 37, which is distantfrom the optical axis LA by a distance H31, and a portion(high-transmittance region) of the second APD filter 38, which isdistant from the optical axis LA by a distance H41, in this order. Themain ray L5 passes through regions, which are positioned near theoptical axis and have high light transmittance T, of both the first andsecond APD filters 37 and 38.

The upper ray L6 of the oblique luminous flux passes through a portion(low-transmittance region) of the first APD filter 37, which is distantfrom the optical axis LA by a distance H32, and a portion(high-transmittance region) of the second APD filter 38, which isdistant from the optical axis LA by a distance H42, in this order. Thelower ray L7 of the oblique luminous flux passes through a portion(high-transmittance region) of the first APD filter 37, which is distantfrom the optical axis LA by a distance H33, and a portion(low-transmittance region) of the second APD filter 38, which is distantfrom the optical axis LA by a distance H43, in this order. Since each ofthe upper ray L6 and the lower ray L7 passes through thelow-transmittance region and the high-transmittance region once, theamount of the reduced upper ray L6 and the amount of the reduced lowerray L7 are equal to each other. Accordingly, a deviation is notgenerated in a blurred image that is generated by the oblique luminousflux.

Since the first APD filter 37 is disposed closest to an end of the lensbarrel 35 and the second APD filter 38 is disposed closest to abase endof the lens barrel 35 in the second embodiment, the upper ray L6 and thelower ray L7 can be reduced equally even in a case in which the main rayL5 of the oblique luminous flux passes through a portion of thediaphragm deviating from the vicinity of the optical axis LA. Since themain ray L5 of the oblique luminous flux is likely to deviate from aportion of the diaphragm 16 in the vicinity of the optical axis LA asthe first and second lens optical systems 12 and 13 are moved by afocusing operation or the like, the second embodiment is effective in acase in which a subject present at an extreme position, such as asubject present substantially at infinity or a near subject, is focused.

A case in which a subject present at an extreme position, such as asubject present substantially at infinity or a near subject, is focusedis a case in which an imaging magnification is extremely low orextremely high. Oblique luminous flux, which passes through thesubstantially upper region of the first APD filter 37, passes throughthe substantially lower region of the second APD filter 38, and has alarge inclination angle with respect to the optical axis LA, is incidentin this case. Since the above-mentioned dichotomized filter has beenused as each of the first and second APD filters 37 and 38 in the secondembodiment, it is possible to more reliably and significantly reduce theupper ray L6 and the lower ray L7 than the main ray L5 even in the caseof oblique luminous flux having a large inclination angle with respectto the optical axis LA.

Third Embodiment

A combination of a set of APD filters of the first embodiment (the firstand second APD filters 17 and 18) and a set of APD filters of the secondembodiment (the first and second APD filters 37 and 38) may be used. Asshown in FIG. 9, a lens barrel 40 of a third embodiment includes boththe same set of APD filters as those of the first embodiment and thesame set of APD filters as those of the second embodiment.

The lens barrel 40 includes a filter insertion/retreat unit 41. Thefilter insertion/retreat unit 41 inserts and retreats the APD filters 17and 18 and the APD filters 37 and 38. The filter insertion/retreat unit41 can take a first insertion state where the APD filters 17 and 18 aresimultaneously inserted and a second insertion state where the APDfilters 37 and 38 are simultaneously inserted.

An imaging device body 50 of the third embodiment has a structure inwhich an insertion/retreat control unit 51 is added into the controlsection 24 of the imaging device body 20 of the first embodiment. Theinsertion/retreat control unit 51 controls the insertion/retreat of theAPD filters performed by the filter insertion/retreat unit 41. The lensbarrel 40 is detachably mounted on the imaging device body 50, and thelens barrel 40 and the imaging device body 50 are used as an imagingdevice 60 of the third embodiment. Since other structures of the thirdembodiment are the same as those of the first or second embodiment, thedetailed description thereof will be omitted.

The insertion/retreat control unit 51 switches the first insertion stateand the second insertion state according to the diaphragm value of thediaphragm 16 or an imaging magnification. Since the second insertionstate is preferable in a case in which the diaphragm value of thediaphragm 16 is close to an open value and an imaging magnification isextremely low or extremely high, the insertion/retreat control unit 51controls the insertion/retreat of the APD filters so that the secondinsertion state is made. In other cases, the insertion/retreat controlunit 51 controls the insertion/retreat of the APD filters so that thefirst insertion state is made.

The control method of the insertion/retreat control unit 51 using thefilter insertion/retreat unit 41 is not limited thereto, and can beappropriately determined according to the characteristics of the firstAPD filter 17, the second APD filter 18, the first APD filter 37, thesecond APD filter 38, the first lens optical system 12, and the secondlens optical system 13.

Fourth Embodiment

The APD filters having unique optical characteristics have been used inthe third embodiment, but APD filters having variable opticalcharacteristics may be used. As shown in FIG. 10, a lens barrel 70 of afourth embodiment includes a first APD filter 73, a second APD filter74, a first APD filter 77, and a second APD filter 78, which havevariable optical characteristics, instead of the four APD filters of thethird embodiment.

Two kinds of materials having different refractive indexes are providedwith an interface, which has a variable shape, (variable-shapeinterface) interposed therebetween, so that each of these four APDfilters having variable optical characteristics is formed. Since theshape of the variable-shape interface can be electrically controlled,the optical characteristics of each APD filter can be controlled.

The lens barrel 70 includes a shape changing unit 71 instead of thefilter insertion/retreat unit 41 of the third embodiment. The shapechanging unit 71 changes the shape of the variable-shape interface ofeach APD filter. The shape changing unit 71 changes the opticalcharacteristics of each APD filter by changing the shape of eachvariable-shape interface.

An imaging device body 80 of the fourth embodiment includes a filtercontrol unit 81 instead of the insertion/retreat control unit 51 that isprovided in the control section 24 of the imaging device body 50 of thethird embodiment. The filter control unit 81 controls the change of theoptical characteristics of each APD filter that is performed by theshape changing unit 71. The lens barrel 70 is detachably mounted on theimaging device body 80, and the lens barrel 70 and the imaging devicebody 80 are used as an imaging device 90 of the fourth embodiment. Sinceother structures of the fourth embodiment are the same as those of thethird embodiment, the detailed description thereof will be omitted.

In the fourth embodiment, it is possible to take the same state as thefirst insertion state of the third embodiment by setting the opticalcharacteristics of the first and second APD filters 73 and 74 to thesame optical characteristics as the optical characteristics of the firstand second APD filters 17 and 18 and setting the optical characteristicsof the first and second APD filters 77 and 78 to optical characteristics(uniform transmittance) that are obtained while APD filters are notprovided.

Further, it is possible to take the same state as the second insertionstate of the third embodiment by setting the optical characteristics ofthe first and second APD filters 77 and 78 to the same opticalcharacteristics as the optical characteristics of the first and secondAPD filters 37 and 38 and setting the optical characteristics of thefirst and second APD filters 73 and 74 to optical characteristics(uniform transmittance) that are obtained while APD filters are notprovided.

That is, in the fourth embodiment, the same control as the switching ofthe first and second insertion states of the third embodiment can beelectrically performed by the filter control unit 81.

Examples of the lens barrel-interchangeable imaging device have beendescribed in the embodiments, but the invention can also be applied tonot a lens-interchangeable imaging device but an integrated imagingdevice, a mobile phone with a camera, and a smartphone.

Explanation of References

-   -   10, 35, 40, 70: lens barrel    -   12: first lens optical system    -   13: second lens optical system    -   16: diaphragm    -   17, 37: first APD filter    -   18, 38: second APD filter    -   20, 50, 80: imaging device body    -   21: imaging element    -   30, 60, 90: imaging device    -   41: filter insertion/retreat unit    -   51: insertion/retreat control unit    -   71: shape changing unit    -   81: filter control unit

What is claimed is:
 1. A lens barrel comprising: a lens optical system that includes a focus lens forming an image with an incident ray; a diaphragm that changes the amount of the incident ray and emits the incident ray; a first apodization filter that is disposed on a light-incident side of the diaphragm and disposed closest to an end of the lens barrel; and a second apodization filter that is disposed on a light-emitting side of the diaphragm and disposed closest to a base end of the lens barrel.
 2. The lens barrel according to claim 1, wherein the first and second apodization filters have optical characteristics in which light transmittance is reduced toward an outer peripheral portion from an optical axis.
 3. The lens barrel according to claim 2, each of the first and second apodization filters has a high-transmittance region and a low-transmittance region.
 4. The lens barrel according to claim 1, wherein a ratio of a diameter of the first apodization filter to that of the second apodization filter is substantially equal to a ratio of a first optical distance between the diaphragm and the first apodization filter to a second optical distance between the diaphragm and the second apodization filter.
 5. An imaging device body on which the lens barrel according to claim 1 is detachably mounted, the imaging device body comprising: an imaging element that generates an imaging signal by photoelectrically converting a ray having passed through the first and second apodization filters.
 6. An imaging device comprising: the lens barrel according to claim 1; and an imaging device body on which the lens barrel is detachably mounted, the imaging device body including an imaging element that generates an imaging signal by photoelectrically converting a ray having passed through the first and second apodization filters. 